Conventionally, when an image or the like is printed on a printing laminate using a sublimable dye, the printing is conducted first on paper using an ink containing the sublimable dye, and then the printed surface of the paper is applied to a surface of the printing laminate and the printed surface of the paper is brought into intimate contact with the printing laminate by means of a heat vacuum applicator, a heated roll or the like so as to conduct thermal compression for allowing the sublimable dye to penetrate the inside of the printing laminate. As another conventional method, printing is conducted using an ink containing a sublimable dye with respect to a temporary displaying surface layer, which is provided at a surface of a printing laminate in order to accept the ink, followed by heating so as to allow the dye to diffuse and penetrate inside the printing laminate, whereby a printed image to be attained can be realized. During the printing, the dye that is sublimated to have a molecular size penetrates the inside of a resin, so that an image is printed by developing colors in a colorable resin layer. In this step, however, if the transfer temperature and the transfer time are lower and shorter than the optimum conditions for the transfer printing, sufficient density of the colors cannot be obtained. Alternatively, if they are in excess of the optimum conditions, problems occur in which the sublimable dye extends to penetrate and migrate into a layer continuous with the colorable resin layer, such as a glue layer and an adhesive layer that are provided for the attachment to a substrate, which impairs the sharpness of the image or makes the edge of the image blurred. In addition, even when the printing is conducted by sublimation dyeing under the optimum conditions, the dye gradually migrates to the afore-mentioned layers that are continuous with the colorable resin layer over the course of time. This means the diffusion of the dye that is to be kept within the colorable resin layer, which causes the problems of discoloration, the blurred edge of an image and the like. As a conventional example, when a printing laminate is manufactured, a colorable resin layer, a surface resin layer and the like are laminated successively on a substrate film made of polyester, etc., so as to manufacture the printing laminate, which is proposed in JP 2002-79751 A, for example.
However, the technology of JP 2002-79751 A has the problem that, when a polyester film used is not stretched, the migration of a dye cannot be prevented. When a biaxially stretched polyester film is used, the interlayer migration of the dye can be prevented to some extent because the biaxially stretched polyester film has an enhanced crystallinity and intermolecular density of the resin due to the stretching. However, such a film also is insufficient for keeping the sharpness of an image for a long time within the colorable layer, and the edge of the printed image becomes blurred in a short time. Furthermore, when a biaxially stretched polyester film is adopted as a substrate used in the course of the manufacturing process, the biaxially stretched polyester film contracts due to the heat applied during the sublimation dyeing, which causes a problem that wrinkles and streaks occur in the printing laminate.
In addition, in the case where the biaxially stretched polyester film is to be attached on a three-dimensionally curved surface, for example, for wrapping vehicles, it becomes difficult to attach the film on the curved surface because the film lacks flexibility, elongation percentage and the like because of its stiffness. Thus, there is a demand in the market for developing a novel printing laminate used for sublimation dyeing that can keep the density of colors of an image for a long time period and can keep the sharpness of the image, is free from wrinkles and streaks that might occur during the heating for transfer and has excellent suitability for the attachment on a three-dimensionally curved surface.